The presently known dielectric substances generally require sintering temperatures above 1000.degree. C., frequently even above 1200.degree. C. These known ceramic dielectrics are described, for example, in Germ. Pat. No. 977,695, Brit. Pat. No. 598,038, DAS No. 1,646,724, DOS Nos. 2,039,835, 2,264,260, 1,918,021 and DAS No. 1,646,723.
If the ceramic dielectric is to be provided with electrodes, they must be applied, because of the high finish-burning temperature of the dielectric, in a second burn at a lower temperature compatible with the metal electrodes.
When electrodes are also required in the interior of the dielectric, as, for example, in multilayer capacitors, the inner electrodes must withstand the finish-burning temperature of the dielectric. This is at present only possible with platinum metals. A progressive, economical production technique requires, however, more and more storing of the electrodes together with the finish burn. The utilizability of cheaper metals than platinum, e.g., silver or base metals, for the electrodes, is gaining increasing interest today. Since the properties of the pure metals can not be influenced, and alloys always have a lower melting point than their individual components, the only way to achieve lower finish-burning temperatures is to influence the properties of the ceramic materials in such a way that the finish-burning temperature is reduced and can be adapted to the electrode material used.
Various methods have been used for a long time for reducing the finish-burning and sintering temperatures. They are based on the use of glass additives or fluxes, which facilitate the sintering of the powdered raw materials. However, the dielectric constant necessarily drops, and the other electric characteristics do not always attain values technically required today.
Thus, for example, Canadian Pat. No. 920,348 describes a capacitor-dielectric of glass and ceramic powder, whose ferro-electric base material consists of TiO.sub.2, BaTiO.sub.3 and ZrO.sub.2 and which is finish-burnt at temperatures between 650.degree. and 900.degree. C. Only low dielectric constants with temperature coefficients of the dielectric constant between 0 and -750 .times. 10.sup.-6 deg.sup.-1 can be obtained.
The object of this invention is to overcome the problem of providing a densely-sintered ceramic dielectric where the drop of the dielectric constant necessarily resulting from the addition of sintering aids is reduced, while the temperature dependence of the dielectric constant remains substantially linear, and the loss factor is less than or at most equal to 10.sup.-3, while permitting the use of wide conditions with regard to sintering temperature and firing interval.